The long-term objective of this investigation is directed towards understanding more fully the potential mechanism(s) whereby virus-determined surface antigens influence lymphoid cell proliferation and malignant growth. This objective encompasses studies concerned with the two following interrelated problems: 1. The chemical nature and mechanism of synthesis and assembly of the Moloney leukemia virus-induced cell surface antigen (MCSA) on mouse lymphoma cells and in immunoresistant sublines; 2. the molecular differences in membranes from Epstein-Barr virus (EBV) negative lymphoma lines and their in vitro EBV-transformed sublines. Current goals are a logical continuation of studies currently in progress which are examining two specific questions: 1. What are the structural changes in MCSA isolated from immunoresistant sublines? 2. What are the specific surface differences which result from the presence of the Epstein-Barr virus in human lymphoma lines? Since many alterations in the cell surface have been implicated in malignant growth, knowledge of the molecular mechanisms underlying these processes may contribute significantly to our understanding of recurrence and metastasis in human cancer.